caching.js

const express = require('express')

const app = express()
const port = 3000
const recursive = function (req, res) {
  counter ++
  setTimeout(recursive, 300);
}

recursive()

var counter = 0

app.get('/', (req, res) => { 
  console.log(`Counter: ${counter}`) 
  res.set('Cache-Control', 'public, max-age=110')
  res.send(`Response: ${counter}`)
})

app.listen(port, ()=> console.log(`listening at http://0.0.0.0:${port}`))